Fix character not sliding on slopes when stop_on_slopes is false.

[yosoyfreeman]

Allows the character to slide on the floor as a result of downwards vertical velocity if stop_on_slopes is set to false.

Fixes 83673

The change is very small, as the issue was that stop_on_slopes was simply not being used at all when handling sliding on slopes.

TODO:
-Check if the same problem exist in 2D and implement the same fix.

Pre PR:
stop_on_slopes has no effect at all on stopping on slopes.

2024-11-27.00-53-52.mp4

Post PR:

The character slides as expected.

2024-11-27.00-50-10.mp4

NOTES:

Q: Why the character was sliding a super tiny bit if we didn't had the functionality in the first place?
A: Because p_cancel_sliding is used wrong in various places (Similar case to #99397), I hope to address that soon.

MPR:

stop_on_slopes_fix.zip

[yosoyfreeman]

Hi there! I been testing this as thoroughly as i can to make sure there are no compatibility issues.

Right now, the fix works quite well, and produces a very natural result. However, it can cause (correctly) the body to get some upwards direction as a consequence of sliding with the floor. Not a bug, but doesn't follow the design philosophy of the whole CharacterBody (No vertical input, no vertical output)

I'm working on testing a couple different ways to approach the same thing while respecting that rule, even if that results in somewhat of a less natural slide, as i understand that right now we have to focus ourselves on fixing errors in the current algorithm, not to change the behavior itself.

I'll update this as soon as i can with the news and test results. I may be over cautious but i really want this to feel like it was there from the beginning, to work in a similar fashion to our current approach (For better or worse) and that it can't cause any kind of regressions.

[yosoyfreeman]

Updated the PR to prevent the floor sliding from adding vertical motion to the body. As i said, bit less natural, but more coherent with the whole thing.

Videos:

2024-11-30.12-32-11.mp4

2024-11-30.12-32-34.mp4

As you can see the lack of #99731 causes some instability in the body. That pr fixes bodies with stop_on_slopes from attempting to re-snap to things is already close enough.